A method for analyzing flooding inside buildings

Abstract

The present invention provides a method for analyzing internal flooding of a building. The method mainly analyzes internal flooding of a building according to determinism, and stipulates and analyzes the analysis of the list of protective equipment, the division of flooding zones, the selection of flooding sources, the analysis method of the flooding source spreading path, etc., and finally forms a hazard evaluation of internal flooding of a nuclear island. In combination with the hazard evaluation, necessary protective measures are taken to ensure that the internal facilities of the building will not be harmed by internal flooding. The present invention adopts deterministic water level analysis, strictly follows the 30-minute non-intervention time for personnel, and the specific flow data and location information of the water source are analyzed and calculated, thereby obtaining water level information that is more in line with reality, which is of great significance to the protection of equipment and the safety of power plants.

Description

Technical Field

[0001] The invention belongs to the design technology of nuclear island plant of nuclear power plant, and specifically is a method for analyzing internal flooding of a building for a nuclear island plant. Background Art

[0002] "HAD102 / 04 Section 4 Protection against internal missiles and their secondary effects in nuclear power plants" stipulates that when powerful missiles may hit pipes, tanks and pools that usually contain liquids, the potential for damage caused by flooding must be evaluated. The internal flooding caused by external flooding in the Fukushima incident also attracted the attention of the National Nuclear Safety Administration and industry experts.

[0003] Taking the M310 main reactor type currently in service in my country as an example, although its internal flooding protection design has been analyzed from a deterministic perspective, no quantitative analysis and conclusions have been made on several key technologies in the analysis method. In order to meet the higher requirements of internal flooding protection design and the requirements for improvement of nuclear power plants under construction proposed by the Nuclear Safety Administration, it is necessary to sort out the links of internal flooding analysis of buildings and strictly standardize the analysis methods of each link in the analysis process, so as to provide a theoretical basis and guarantee for the analysis and research of internal flooding of nuclear islands.

[0004] Chinese patent application 201611144681.4 discloses a system and method for dividing flooding zones in a nuclear power plant. The method divides the area into flooding zones according to the distribution of flooding sources and important equipment in the nuclear power plant area, and then calculates the flooding level in each flooding zone. According to the impact of the flooding level on the important equipment in the corresponding zone, the existing zone is determined or the flooding zone is optimized and adjusted, so as to effectively isolate the equipment and components of different safety series that perform the same safety function, and avoid the common mode failure of different series of equipment that perform a certain safety function caused by the same flooding. The method divides the flooding zones according to the civil structure, room layout, and system layout of the nuclear island plant. The calculation of the flooding level is only based on the total flooding flow minus the drainage flow, and then divided by the net floor area. It is impossible to simulate and analyze the flooding process inside the nuclear island plant. The calculation of the flooding level is not accurate enough, and it is difficult to reflect the actual situation of flooding inside the nuclear island after the accident. Summary of the invention

[0005] The purpose of the present invention is to provide a comprehensive and complete method for analyzing internal flooding of buildings in view of the defects of the prior art, to provide a solid theoretical basis for each step of the internal flooding analysis process, and to ensure the rationality of the entire analysis method.

[0006] The technical solution of the present invention is as follows: A method for analyzing flooding inside a building, comprising the following steps:

[0007] (S1) Determine the list of equipment that needs protection by analyzing various safety-related systems and equipment;

[0008] (S2) Combine the various plant buildings inside the building with the fire protection zones and radiation zones to divide them into reasonable flood zones, and conduct independent flood analysis within the zones;

[0009] (S3) Selecting reasonable and representative flood sources in each flooding area;

[0010] (S4) determine the flow rates of representative flooding sources;

[0011] (S5) Modeling a hydrodynamic mathematical model based on the SPH method, calibrating and verifying the hydrodynamic mathematical model through a physical test model, and obtaining real-time data of the drainage spreading process;

[0012] (S6) Combining the analysis results of step (S1) and step (S5), a flood analysis report is obtained, and necessary protective measures are taken for equipment that needs to be protected and is at risk of flooding.

[0013] Furthermore, in the above-mentioned internal flooding analysis method of a building, in step (S1), the protective equipment is screened according to the safety requirements of the nuclear power plant, decomposed according to the final safety goal of the research object, and the following are analyzed one by one to finally determine the list of protective equipment required.

[0014] a) Determine the protective equipment according to the system functions to meet the conditions for coolant release and main pump seal injection;

[0015] b) Ensure that the equipment including the reactor shutdown, boronization and residual heat removal functions in the cold and hot stages operate normally;

[0016] c) Ensure the normal operation of the ventilation system under accidents and the equipment under the dedicated safety facility system;

[0017] d) Ensure that the main control room and its surrounding environment remain in a strictly flood-proof state during flood analysis.

[0018] Further, in the above-mentioned method for analyzing flooding inside a building, the specific method for dividing the flooding zones in step (S2) is as follows:

[0019] If fireproof or waterproof sealed doors are installed at the connecting positions between the powerhouses in the nuclear island, the water sources between the powerhouses will not flow to each other, and the powerhouse will be divided into the preliminary flooding zone analysis range; if there is no such installation between the powerhouses, the connecting passage and the powerhouse as a whole will be divided into the preliminary flooding zone analysis range;

[0020] Secondly, if there are fire partitions inside the factory building, and the holes and doors in the fire partitions are connected to other fire partitions with fire blocking, fire doors, and semi-airtight doors, and these fire blocking, fire doors, and semi-airtight doors can withstand a certain atmospheric pressure and have the function of blocking water sources, then each fire partition is equivalent to a confined space, and the fire partition is analyzed as an independent flooding partition;

[0021] If the fire partition involves radiation partitions, and the holes and sleeves in a compartment are sealed with biological protection, the water source will not flow out within the time limit of the flooding analysis. A compartment or several small compartments can be analyzed as independent flooding partitions.

[0022] Furthermore, in the above-mentioned internal flooding analysis method of a building, in step (S3), a reasonable and representative flooding source is selected according to the pipe damage, fire water sprinkler and water tank failure; when multiple flooding sources exist in a single flooding zone, the most dangerous flooding source is taken as the analysis point to ensure that the water level in the flooding zone is the highest water level.

[0023] Further, in the above-mentioned method for analyzing internal flooding of a building, the calculation formula for the outflow rate of the pipe breach in the flooded zone in step (S4) is:

[0024]

[0025] In the formula, q v is the breach flow,

[0026] C q is the flow coefficient,

[0027] A is the flow area of ​​the breach,

[0028] ΔP is the pressure difference,

[0029] ρ is the fluid density.

[0030] The outflow of water sources in independent flooded areas shall be handled as follows:

[0031] 1) The ground drainage facilities are treated as blocked, and the outflow is 0;

[0032] 2) Other unblocked holes such as door openings and ground holes are treated as hole leakage flow; blocked holes are divided according to the flooding zoning method in step (S2) to determine the outflow of the flooding zone.

[0033] Further, in the above-mentioned building internal flooding analysis method, the specific simulation method of step (S5) is as follows:

[0034] (S5-1) Conduct physical experiments according to the simulation conditions as a basis for verifying the mathematical simulation results;

[0035] (S5-2) Modeling a hydrodynamic mathematical model based on the SPH method according to the building-related information and the flood source information;

[0036] (S5-3) Calibrate and verify the hydrodynamic mathematical model based on the test results of the physical test model;

[0037] (S5-4) Use a verified hydrodynamic mathematical model to carry out flooding event simulation calculations according to calculation requirements;

[0038] (S5-5) The change of water level over time during the flooding process is quantified based on the simulation calculation results, and a three-dimensional dynamic demonstration is produced.

[0039] Furthermore, in step (S5-1) of the above-mentioned method for simulating internal flooding of a building, the model of the physical test is designed according to the gravity similarity criterion based on the structural characteristics of the building and the flow and location information of the internal flooding source, and the length scale of the model is determined in combination with the test structure scale and equipment performance, and the flow and roughness that meet the test conditions are set to carry out the flooding test.

[0040] Furthermore, in step (S5-2) of the above-mentioned method for simulating flooding inside a building, the hydrodynamic mathematical model is modeled using DualSPHysics software;

[0041] The plant and related foundations and equipment structures are used as the solid wall boundaries of the model. Only the fluid particles in the plant are considered in the calculation. The particle motion is controlled by the continuity equation, momentum equation and state equation. In the Cartesian coordinate system, the control equation is as follows:

[0042]

[0043]

[0044]

[0045] Where: t is time; v is fluid velocity; ρ is fluid density; ρ O is the reference density; m is the fluid mass; P is the pressure; Π is the viscosity term; W is the kernel function; g is the gravitational acceleration; C0 is the speed of sound at the reference density; γ is a constant coefficient; subscript i represents the i-th particle, subscript j represents the j-th particle within the scope of action of particle i; subscript ij represents the interaction relationship between the i-th particle and the j-th particle within its scope of action; subscript 0 is a constant subscript.

[0046] Furthermore, in step (S5-3) of the above-mentioned method for simulating internal flooding of a building, the physical model test results and the hydrodynamic mathematical model calculation results are sorted out, the water spread state and water level height data of the two are compared, and the mathematical model parameters are adjusted, so as to finally achieve a situation where the flooding effects of the two are basically the same.

[0047] Furthermore, in step (S5-4) of the above-mentioned method for simulating flooding inside a building, the flooding event simulation calculation is completed using parallel technology on a computer equipped with a professional GPU scientific computing acceleration device.

[0048] Furthermore, in step (S5-5) of the above-mentioned method for simulating internal flooding of a building, by extracting the calculation result file of the DualSPHysics software, the change of the water level over time during the flooding process is quantified to obtain the room flooding height, the time curve of the flooding height and the water spread path.

[0049] Furthermore, in the above-mentioned method for analyzing internal flooding of a building, in step (S6), the mathematical simulation results and the list of equipment to be protected are combined to determine the impact of the flooding height in the flood analysis area on the protective equipment. If there is no impact, the flooding condition is considered safe; if the flooding height is higher than the allowable range of the equipment to be protected, appropriate protective measures must be taken to ensure that the main safety functions are not lost.

[0050] The beneficial effects of the present invention are as follows: The present invention conducts a detailed analysis from the aspects of the analysis of protective equipment, the division of flooding zones, the screening method of flooding sources, and the analysis of the spreading path of flooding sources, thereby ensuring the integrity and rationality of the internal flooding analysis method of the nuclear island plant. The deterministic water level analysis is adopted, and the specific flow and location information of the water source are analyzed and calculated strictly in accordance with the 30-minute non-intervention time of personnel, so as to obtain more practical water level information, which is of great significance to the protection of equipment and the safety of power plants. The present invention ultimately forms a hazard assessment of internal flooding in the nuclear island, and takes necessary protective measures in combination with the hazard assessment, thereby ensuring that the safety-related systems, equipment and related facilities of the nuclear island will not affect the function of safe shutdown due to internal flooding, thereby reducing the hazards of internal flooding events. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 A flow chart of the internal flooding analysis method for a building provided by the present invention;

[0052] Figure 2 This is a flow chart of a method for establishing a hydrodynamic mathematical model for flooding simulation based on the SPH method of the present invention;

[0053] Figure 3 A schematic diagram of the basic components of a water flow control device of a flooding simulation physical test model in the present invention;

[0054] Figure 4 It is a comparative schematic diagram of the water level change history results of a certain characteristic point in the flooding simulation test of the present invention. DETAILED DESCRIPTION

[0055] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0056] The present invention provides a complete analysis method for internal flooding of nuclear island plants. The analysis method analyzes from the aspects of analysis of protective equipment, division of flooding zones, screening method of flooding sources, analysis of flooding source spreading paths, etc., providing a solid theoretical basis for each step of the internal flooding analysis process and ensuring the rationality of the entire analysis method.

[0057] like Figure 1 As shown, a method for analyzing flooding inside a building comprises the following steps:

[0058] (S1) Determine the list of equipment that needs protection by analyzing various safety-related systems and equipment;

[0059] (S2) Combine the various plant buildings inside the building with the fire protection zones and radiation zones to divide them into reasonable flood zones, and conduct independent flood analysis within the zones;

[0060] (S3) In each flooding zone, select reasonable and representative flooding sources based on pipeline damage, fire sprinkler and water tank failure;

[0061] (S4) determine the flow rates of representative flooding sources;

[0062] (S5) Modeling a hydrodynamic mathematical model based on the SPH method, calibrating and verifying the hydrodynamic mathematical model through a physical test model, and obtaining real-time data of the drainage spreading process;

[0063] (S6) Combining the analysis results of step (S1) and step (S5), a flood analysis report is obtained, and necessary protective measures are taken for equipment that needs to be protected and is at risk of flooding.

[0064] Each method step is described in detail below.

[0065] 1. Analysis of protective equipment list

[0066] First, to ensure that the main safety functions are not lost when the nuclear island building is flooded, the internal flooding analysis of the nuclear island must include all equipment that needs to perform safety functions. In the internal flooding analysis, if the safety-related systems, structures and components do not have a safe shutdown function or the safe shutdown function has been completed when they fail, their failure is acceptable.

[0067] In flooding analysis, the first thing to do is to screen the protective equipment according to the safety requirements of the nuclear power plant, which involves a large number of equipment in the main circuit system, various auxiliary systems, and electrical instrumentation and control systems.

[0068] According to the ultimate safety goal of the research object, the following are analyzed one by one:

[0069] a) Determine the protective equipment according to the system functions to meet the conditions for coolant release and main pump seal injection.

[0070] b) Ensure that the equipment including functions such as reactor shutdown, boronization, and residual heat removal in the cold and hot stages operate normally.

[0071] c) Ensure the normal operation of the ventilation system under accidents and the equipment under the dedicated safety facility system.

[0072] d) Ensure that the main control room and its surrounding environment remain in a strictly flood-proof state during flood analysis.

[0073] Finalize the list of protective equipment required.

[0074] 2. Division of flooded areas

[0075] The division rules of flooded zones are that fireproof or waterproof sealed doors are set at the connecting positions between the various powerhouses in the nuclear island, and the water sources between the powerhouses will not flow to each other. Therefore, the analysis scope is first narrowed to a certain powerhouse. If there is no such setting between the powerhouses, it is necessary to analyze the connecting passages and the powerhouse as a whole; secondly, fire partitions are set inside the powerhouse, and the holes, doors and other connecting positions within the fire partitions are equipped with fire blocking, fire doors, semi-airtight doors, etc. with other fire partitions. These fire blocking, fire doors and semi-airtight doors can withstand Under a certain atmospheric pressure, it has the function of blocking water sources. Therefore, each fire protection area is equivalent to a confined space, and the analysis scope can be narrowed to a certain fire protection zone. Some fire protection zones involve changes in radiation zones, and radiation shielding and sealing requirements are also required. The shielding effect of biological protection shielding and sealing on gamma rays is equivalent to that of concrete of the same thickness. Therefore, if the holes and sleeves in the compartment are sealed with biological protection, water sources will not flow out within the time limit of flooding analysis. Based on this, the analysis scope can be further narrowed to a certain compartment or several small compartments.

[0076] 3. Screening of flooding sources

[0077] After the analysis scope is determined, further screening of flood sources is carried out. Potential screening is carried out for equipment, pipelines, fire protection, bellows, etc. within a single flood prevention zone in the following manner:

[0078] Equipment: For flooding caused by leakage of active components such as pumps and valves or failure of anti-leakage sealing devices, the leakage caused by the equipment can be compared with the flooding source of pipe rupture or breach in the flooding zone, and the maximum value can be selected.

[0079] Tanks: Seismic Class I tanks with redundant vacuum bursting devices or atmospheric vents and overpressure protection may be assumed to fail. Seismic Class I tanks without these features and all non-seismic Class I tanks should be evaluated for flooding effects.

[0080] Bellows: The bellows and expansion joints of the circulating water system should be specially evaluated. When conducting the evaluation, it should be assumed that each bellows and expansion joint has completely failed, which is equivalent to the rupture mode of the pipeline in which they are located.

[0081] Fire sprinkler: The flooding caused by the triggering of the fire protection system should take into account the impact of all fire protection system actions in the area. The total flow of the sprinkler is calculated according to the relevant requirements of RCC-I and GB / T 22158 design specifications: 10~15L / (min*㎡)*time (30 minutes)*area (room), and the total release amount of the fire hydrant is added. The sprinkler intensity is determined according to different equipment.

[0082] Containment spray: The containment spray water forms a circulating cooling with the internal refueling water tank (IRWST). The plant design will not cause a large amount of water to be retained in the area. No specific analysis is required for the water source.

[0083] High-energy pipelines: There are two forms of high-energy pipelines: breaches and ruptures. However, the amount of water generated by ruptures is much greater than the amount of water generated by leaking cracks or through-wall cracks. Based on the principle of selecting the largest water source, high-energy pipelines only analyze the flooding source caused by the rupture point. High-energy pipelines are assumed to have circumferential ruptures and longitudinal ruptures, but the two do not occur at the same time, so the worst-case double-end rupture is used as the basis for analysis. First, the amount of water under high-energy pipeline rupture is used as the flooding source; secondly, according to the several rupture points obtained by mechanical analysis, the rupture point that poses the greatest threat to the protective equipment in the room is selected as the water source point.

[0084] Medium energy pipeline: The damage position of the medium energy pipeline is only assumed to be a through-wall crack, and there is no possibility of circumferential or longitudinal rupture. Referring to the breach point obtained by mechanical analysis, the breach point that poses the greatest threat to the protective equipment in the room is selected as the water source analysis point. The breach of the medium energy pipeline is a small circular hole that penetrates the pipe wall. Its cross-sectional flow area is equal to the product of half of the inner diameter of the pipe and half of the pipe wall thickness, that is, the cross-sectional flow area is: 1 / 2t*1 / 2D, t represents the pipe wall thickness, and D represents the inner diameter.

[0085] Non-nuclear and non-seismic pipelines: For pipelines that have not undergone seismic analysis, the rupture may occur at each pipe fitting and welded accessory. Similarly, the most unfavorable location in the room is selected as the water source point.

[0086] In a single flood prevention zone, when all the above-mentioned source items exist, the most dangerous water source is taken as the analysis point, thus ensuring that the water level in the zone is the highest.

[0087] 4. Determine the flow rate of representative flood sources

[0088] The outflow rate of the breach is expressed by the formula:

[0089]

[0090] In the formula, q v -Break flow

[0091] C q -Flow coefficient

[0092] A-Break flow area

[0093] ΔP-pressure difference

[0094] ρ - fluid density

[0095] Based on the above analysis, the water inflow within the flood prevention zone has been determined, and the outflow analysis is as follows:

[0096] 1) The ground drainage facilities are treated as blocked, and the outflow is 0;

[0097] 2) Other unblocked holes such as door openings and ground holes are treated as hole leakage flow. Blocked holes are divided according to the flooding zoning method in step (S2) to determine the outflow of the flooding zone.

[0098] 5. Flooding physical test and hydrodynamic mathematical model simulation

[0099] According to the above input conditions, a three-dimensional mathematical model is further established to simulate the hypothetical internal flooding event with a computer to obtain the flooding water level after steady state, as well as the transient maximum water level on the flooding path and the time when the maximum water level is reached. Or for a simple analysis unit, the spreading path and water level of the flooding can be quickly analyzed through manual calculation.

[0100] 5.1) Physical model test:

[0101] In order to determine the reliability of the calculation results of the mathematical model, physical model tests were carried out to help adjust the model parameters, including data such as particle size and time step. By analyzing the structural characteristics of the plant (including building structure, door type, threshold, hole, staircase, etc.) and the flow and location information of the internal flooding source (including flow size and water flow direction), physical model tests were designed according to the gravity similarity criterion, and the structural model of the nuclear island plant was established in proportion. The model length scale was determined in combination with factors such as the test structure scale and equipment performance, and the model was made and tested. High-precision dynamic water level monitoring equipment was used to measure the water level changes at different locations during the flooding time.

[0102] The establishment of a physical model test mainly includes: plant model production, installation and debugging of water flow control equipment, installation of water level measuring instruments and data acquisition software, simulation tests of internal flooding in the plant under different working conditions, and collation and analysis of test data.

[0103] Highly transparent and hard organic glass can be used as the model making material to ensure that the model scale is similar to the prototype geometry. The instruments and equipment required for the test include water flow control equipment and ultrasonic water level measurement system, which can dynamically measure the water level time course curve during flooding. By determining the test flow rate, according to the flow requirements, a high-precision constant water flow control device is customized. The basic components of the water flow control device are as follows: Figure 3 As shown, it includes a water reservoir 1, a water pump 2, an electromagnetic flowmeter 5, a pressure gauge 3, a regulating valve 4, a rubber hose 6, and an expansion / reduction short pipe 7. The data collected by the ultrasonic water level probe and the images recorded by the camera are extracted to analyze the rationality of the test data.

[0104] Each test condition was repeated three times. The specific test steps are as follows:

[0105] ① Debug the water supply system to meet the water discharge requirements at the leakage point;

[0106] ② Lay out pipelines according to the location of the leak;

[0107] ③ Adjust the water level measuring probe in the room with the main flooding path;

[0108] ④ Zero point calibration of water level measurement system;

[0109] ⑤ Set up the camera and determine the shooting content;

[0110] ⑥ Start the test and record the water level changes, maximum flooding height, and flooding path in different rooms;

[0111] ⑦ Drain the water in the model, clean and dry the model, and repeat the test.

[0112] At the end of the test, the data collected by the ultrasonic water level probe and the images recorded by the camera were extracted and analyzed for rationality, and the change of water level over time was plotted as a curve as a basis for mathematical model verification.

[0113] 5.2) Modeling of hydrodynamic mathematical model:

[0114] (1) Establishment of mathematical model:

[0115] According to the building structure, door types, thresholds, holes, stairs and other related information of the nuclear island plant, as well as the flow size and flow direction of the flooding source, the DualSPHysics software based on the SPH method was used for hydrodynamic modeling. DualSPHysics software is an open source software based on the smoothed particle hydrodynamics (SPH) model.

[0116] The plant and related foundations, equipment structures, etc. are used as the solid wall boundaries of the model. Only the fluid particles in the plant are considered in the calculation. The particle motion is controlled by the continuity equation, momentum equation and state equation. In the Cartesian coordinate system, the control equation is described as follows:

[0117]

[0118]

[0119]

[0120] Where: t is time; v is fluid velocity; ρ is fluid density; ρ O is the reference density; m is the fluid mass; P is the pressure; Π is the viscosity term; W is the kernel function; g is the gravitational acceleration; C0 is the speed of sound at the reference density; γ is a constant coefficient; subscript i represents the i-th particle, subscript j represents the j-th particle within the scope of action of particle i; subscript ij represents the interaction relationship between the i-th particle and the j-th particle within its scope of action; subscript 0 is a constant subscript.

[0121] (2) Parameter setting:

[0122] The Quintic kernel form is selected, and the corresponding smoothing scale is selected as 0.866; the Symplectic time integration format is selected, and the variable time step method is used to improve the calculation efficiency, and the corresponding maximum Crown number is set to 0.3; the viscosity treatment method adopts the commonly used artificial viscosity method, and the viscosity coefficient is set to 0.01; the gravity acceleration is set to 9.81m / s 2 ; Water density is set to 1000kg / s 3; The constant coefficient γ in the state equation is set to 7; the Delta-SPH formula is used to increase the diffusion term to reduce density fluctuations, and the Delta-SPH coefficient is set to 0.1; the particles are arranged in a staggered manner on the solid wall boundary.

[0123] 5.3) Calibration and verification of the hydrodynamic mathematical model

[0124] The selection of particle size, time step and model parameters in mathematical model calculation is directly related to the calculation accuracy, efficiency and authenticity of flow state. If the time step and particle size are set too large, the number of particles is small, but the calculation result is of low accuracy, which directly leads to the water level height result not being consistent with the actual situation; if the time step and particle size are set too small, the number of particles required for calculation is abnormally large, and the calculation load far exceeds the capacity of existing computers. Adjusting the parameters of the above mathematical model according to the results of the physical model test can ensure that when a series of mathematical simulations of the flooding time of the plant are carried out later, the results that meet the accuracy requirements can be obtained within a reasonable time range and with relatively economical calculation costs. The physical model test results and the mathematical model calculation results are sorted out, the spreading state of the water body and the water level height data are compared, and the mathematical model parameters are adjusted, so that the flooding effects of the two are basically the same. Figure 4 This is a comparison of the water level change results at a certain characteristic point in the experiment.

[0125] 5.4) Carry out flooding simulation calculation according to calculation requirements:

[0126] After the model is built, it is completed on a computer equipped with a professional GPU scientific computing accelerator (2880 cores). The DualSPHys ics software solver uses advanced and mature SPH algorithms, supports parallel computing of the central processing unit (CPU) or graphics processing unit (GPU), and especially uses GPU-based parallel technology to achieve efficient flow field simulation of tens of millions of particles, meeting the requirements for calculation accuracy and efficiency in actual engineering.

[0127] 5.5) Post-processing of calculation results:

[0128] (1) Data processing

[0129] The data extraction program can be redeveloped through existing technical means, which can be implemented by technicians in this field. The developed data extraction program can read the calculation result file of DualSPHys ics, quantify the change of water level over time during the flooding process, and obtain the room flooding height, the time curve of the flooding height and the water spread path.

[0130] (2) 3D dynamic demonstration

[0131] The calculation results of DualSPHys ics can be directly read by ParaView and made into a 3D demonstration animation. Through the 3D demonstration animation, the flooding of the structures in the building can be intuitively monitored during the flooding process, providing an important basis for the analysis and research of the flooding inside the nuclear island.

[0132] 6. Internal flooding hazard assessment

[0133] The mathematical simulation results are combined with the list of protective equipment to determine the impact of the flood height in the flood analysis area on the protective equipment. If there is no impact, the flood condition is considered safe. If the flood height is higher than the allowable range of the protective equipment, appropriate protective measures must be taken to ensure that the main safety functions are not lost.

[0134] In summary, the present invention has conducted a detailed analysis from the aspects of the determination of protective equipment, the division of flooding zones, the screening method of flooding sources, and the spreading path of flooding sources. The above methods work together to ensure the integrity and rationality of the internal flooding analysis method. Among them, a deterministic water level analysis is adopted, and the specific data and location information of the water source are analyzed and calculated strictly in accordance with the 30-minute non-intervention time of personnel, so as to obtain more realistic water level information, which is of great significance to the protection of equipment and the safety of power plants. The present invention ultimately forms a hazard assessment of internal flooding in the nuclear island, and takes necessary protective measures in combination with the hazard assessment, thereby ensuring that the safety-related systems, equipment and related facilities of the nuclear island will not affect the function of safe shutdown due to internal flooding or reduce the hazards of internal flooding events.

[0135] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for analyzing flooding inside a building, comprising the following steps: S1. Determine the list of equipment that needs protection by analyzing various safety-related systems and equipment; S2. Combine the various factory buildings inside the building with the fire protection zones and radiation zones to divide them into reasonable flood zones, and conduct independent flood analysis within the zones. The specific division method of flood zones is as follows: If fireproof or waterproof sealed doors are installed at the connecting positions between the powerhouses in the nuclear island, the water sources between the powerhouses will not flow to each other, and the powerhouse will be divided into the preliminary flooding zone analysis range; if there is no such installation between the powerhouses, the connecting passage and the powerhouse as a whole will be divided into the preliminary flooding zone analysis range; Secondly, if there are fire partitions inside the factory building, and the holes and doors in the fire partitions are connected to other fire partitions with fire blocking, fire doors, and semi-airtight doors, and these fire blocking, fire doors, and semi-airtight doors can withstand a certain atmospheric pressure and have the function of blocking water sources, then each fire partition is equivalent to a confined space, and the fire partition is analyzed as an independent flooding partition; If the fire partition involves radiation partitions, if the holes and sleeves in a compartment are blocked by biological protection, water will not flow out within the flooding analysis time limit, and a compartment or several small compartments will be analyzed as independent flooding partitions; S3. Select reasonable and representative flood sources in each flood zone; S4. Determine the flow rate of representative flood sources. The calculation formula for the outflow rate of pipeline breaches in the flooded area is: In the formula, q v is the breach flow, C q is the flow coefficient, A is the flow area of ​​the breach, ΔP is the pressure difference, ρ is the fluid density; The outflow of water sources in independent flooded areas shall be handled as follows: 1) The ground drainage facilities are treated as blocked, and the outflow is 0; 2) Unblocked door openings and ground holes are treated according to the hole leakage flow; blocked ones are divided according to the flooding zoning method in step S2 to determine the outflow of the flooding zone; S5, a hydrodynamic mathematical model is built based on the SPH method, and the hydrodynamic mathematical model is calibrated and verified through a physical test model to obtain real-time data of the drainage spreading process. The specific method is as follows: S5-1. Carry out physical tests according to simulation conditions as the basis for verifying the results of mathematical simulation. The model of the physical test is designed according to the gravity similarity criterion based on the structural characteristics of the building and the flow and location information of the internal flooding source. The length scale of the model is determined in combination with the test structure scale and equipment performance, and the flow and roughness that meet the test conditions are set to conduct flooding tests. S5-2. Based on the information about the building and the source of flooding, the hydrodynamic mathematical model was built using DualSPHysics software based on the SPH method. The plant and related foundations and equipment structures were used as the solid wall boundaries of the model. Only the fluid particles in the plant were considered in the calculation. The particle motion was controlled by the continuity equation, momentum equation and state equation. In the Cartesian coordinate system, the control equation is as follows: Where: t is time; v is fluid velocity; ρ is fluid density; ρ O is the reference density; m is the fluid mass; P is the pressure; Π is the viscosity term; W is the kernel function; g is the gravitational acceleration; C0 is the speed of sound under the reference density; γ is a constant coefficient; subscript i represents the i-th particle, subscript j represents the j-th particle within the scope of the i-th particle; subscript ij represents the interaction relationship between the i-th particle and the j-th particle within its scope; subscript 0 is a constant subscript; S5-3. Calibrate and verify the hydrodynamic mathematical model based on the test results of the physical test model; collate the test results of the physical model and the calculation results of the hydrodynamic mathematical model, compare the water spread state and water level height data of the two, and adjust the parameters of the mathematical model to ultimately achieve a situation where the flooding effects of the two are basically the same; S5-4. Use a verified hydrodynamic mathematical model to carry out flood event simulation calculation according to calculation requirements; the flood event simulation calculation is completed using parallel technology on a computer equipped with a professional GPU scientific computing acceleration device; S5-5. By extracting the calculation result file of DualSPHysics software, the change of water level over time during flooding is quantified, the room flooding height, the time course curve of flooding height and the water spreading path are obtained, and a three-dimensional dynamic demonstration is made; S6. Combining the analysis results of step S1 and step S5, a flood analysis report is obtained, and protective measures are taken for equipment that needs protection and is at risk of flooding.

2. The method for analyzing internal flooding of a building according to claim 1, characterized in that: In step S1, the protective equipment is screened according to the safety requirements of the nuclear power plant, decomposed according to the final safety goal of the research object, and analyzed one by one, and finally the list of protective equipment required is determined; a) Determine the protective equipment according to the system functions to meet the conditions for coolant release and main pump seal injection; b) Ensure that the equipment including the reactor shutdown, boronization and residual heat removal functions in the cold and hot stages operate normally; c) Ensure the normal operation of the ventilation system under accidents and the equipment under the dedicated safety facility system; d) Ensure that the main control room and its surrounding environment remain in a strictly flood-proof state during flood analysis.

3. The method for analyzing internal flooding of a building according to claim 1, characterized in that: In step S3, a reasonable and representative flood source is selected according to the pipeline damage, fire water sprinkler and water tank failure. When multiple flood sources exist in a single flood zone, the most dangerous flood source is taken as the analysis point to ensure that the water level in the flood zone is the highest water level.

4. The method for analyzing internal flooding of a building as claimed in claim 1, characterized in that: In step S6, the mathematical simulation results are combined with the list of equipment to be protected to determine the impact of the flood height in the flood analysis area on the protective equipment. If there is no impact, the flood condition is considered safe; if the flood height is higher than the allowable range of the equipment to be protected, protective measures must be taken to ensure that the main safety functions are not lost.

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